LiveActive security incident?Get immediate response
CVE Record

CVE-2021-29505: XStream is vulnerable to a Remote Command Execution attack

XStream is software for serializing Java objects to XML and back again. A vulnerability in XStream versions prior to 1.4.17 may allow a remote attacker has sufficient rights to execute commands of the host only by manipulating the processed input stream. No user who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types is affected. The vulnerability is patched in version 1.4.17.

HighCVSS 7.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

XStream can turn XML back into Java objects. In affected versions, maliciously shaped input may let a remote attacker execute commands on the host if the application processes that input and the attacker has the required access. The vendor states users with a strict minimal-type whitelist are not affected.

Executive priority

Prioritize remediation for systems that accept external or semi-trusted XML input, because successful exploitation can compromise host confidentiality, integrity, and availability. This is not marked as known exploited in the supplied data, but the potential impact justifies timely patching and configuration review.

Technical view

CVE-2021-29505 affects XStream before 1.4.17 and is categorized as unsafe deserialization/code injection, CWE-502 and CWE-94. The CVSS 3.1 score is 7.5, with network attack vector, high complexity, low privileges, and high confidentiality, integrity, and availability impact. Version 1.4.17 contains the patch.

Likely exposure

Exposure is most likely in Java applications or packaged products using XStream before 1.4.17 to process XML or object streams influenced by users, integrations, queues, files, or APIs. Risk is lower where XStream's security framework uses a minimal whitelist of allowed types.

Exploitation context

The bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation is described as remote command execution through manipulated input, but the CVSS vector indicates high complexity and required privileges. Treat internet-facing or partner-facing deserialization paths as higher priority.

Researcher notes

Focus validation on XStream version, deserialization entry points, and security framework configuration. Do not assume every XStream use is exploitable; the vendor says strict whitelist users are unaffected. Evidence in the bundle supports the affected range and fix, but not active exploitation or product-specific exposure beyond listed advisories.

Mitigation direction

  • Upgrade XStream dependencies to version 1.4.17 or later.
  • Use XStream's security framework with a minimal required type whitelist.
  • Update vendor or operating system packages that bundle XStream.
  • Prioritize systems processing untrusted XML or serialized object streams.
  • Check product advisories where XStream is embedded indirectly.

Validation and detection

  • Inventory direct and transitive XStream versions across Java applications.
  • Confirm runtime packages do not include XStream before 1.4.17.
  • Review code paths that deserialize XML from users, files, APIs, or queues.
  • Verify XStream allowlists restrict processing to required application types.
  • Check vendor advisories for packaged software using XStream.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-502: Code execution behavior lookup

Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · medium confidence lookup

CWE-94: Code execution behavior lookup

Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-29505 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
20Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H1.65.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-29505Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
x-streamxstream< 1.4.17Listed
Weakness

CWE details

CWE-502CWE-94

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.